Yo Bonehead! Sorry, couldn't resist! Actually, they are ALL workable. It just depends on what you want to make, and the size pieces you have available. The low carbon steels work well for anything ornamental, or not needing strength. Higher carbon can be used for knives or tooling, depending on carbon content.
If you are a begginer, than stick with low carbon. And as a beginner, you will probably be using a hand hammer, not a power hammer. And lower carbon steels work much easier than high carbon. Now, 1018 is a low carbon steel, moves easily, and great for a lot of ornamental work. A36 is a higher carbon steel, meeting minimun structural requirements. That is what is normally sold at hardware and box stores. And what a lot of us use. It may contain higher carbon, but usuallly not enough to fully harden for something like a knife. Very usefull steel, and very common. Works well for tongs. Around here, 1018 is a special order steel. What I buy at the steel yard is A36.
Something like 5160 or higher will be used for knives, tooling, spring fullers, hardie tools, etc. The higher carbon, more care must be taken to work within the proper ranges of heat for that steel.
Tell us what steels you can scrounge, and maybe we can be more specific.